The invention relates to a pre-cylinder signature collector in a web press having cutting cylinders for cutting a web into signatures and a transfer cylinder for receiving the signatures.
A web press can print multiple images around the circumference of an impression cylinder. If signatures containing the images are cut from the web and collected together in a folding process, then a collect cylinder is required. The collect cylinder grips a cut signature and transports it completely around the cylinder so that it can be combined with a signature from a different part of the impression cylinder. That process continues until the total number of signatures are collected, and then the collected signatures are transferred from the collect cylinder to the next stage of the process, usually a jaw cylinder.
The problem with that approach is that the size of the collect cylinder s dictated by the number of signatures that will be collected. If the impression cylinder is printing two signatures around, then the collect cylinder cannot be made of an even number of gripper parts. If the impression cylinder is printing three signatures around then the collect cylinder can not be 3, 6, 9, or any multiple of three gripper parts around. That coupling between the desired number of collected signatures and the number of parts on the collect cylinder forces the collect cylinder to be very large and expensive in order to accommodate different collected signatures from the same cylinder.
Another problem with the current approach is that the signatures must remain single-spaced on the collect cylinder so that a gripper can grip the leading edge of all of the signatures that will be collected to form an output. That requirement does not allow the signatures to slow down as they are being transported by the collect cylinder because the signatures would become imbricated.
U.S. Pat. No. 4,746,107 and German Published, Non-Prosecuted Patent Application DE 35 27 710 A1 are cited as showing devices which are representative of such prior art devices.
It is accordingly an object of the invention to provide a pre-cylinder signature collector, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which collects the signatures before they arrive at the transfer cylinder.
With the foregoing and other objects in view there is provided, in accordance with the invention, in a web press having cutting cylinders for cutting a web into signatures and a transfer cylinder for receiving the signatures, a pre-cylinder signature collector, comprising a diverter station for diverting the signatures received from the cutting cylinders; at least two tape paths having different lengths for receiving the signatures from said diverter station; and at least one collection point for collecting the signatures from all of said tape paths on top of one another for passage to the transfer cylinder.
There are multiple paths from the cutting cylinder to the transfer cylinder. The length of these paths and the number of paths are determined by the desired number of signatures to be collected to form the output.
If the impression cylinder is two signatures around then there would be two different paths from the cutting cylinder to the collect cylinder, path xe2x80x9cAxe2x80x9d and path xe2x80x9cBxe2x80x9d. If the length of path xe2x80x9cAxe2x80x9d is X then the length of path xe2x80x9cBxe2x80x9d would be (X plus P) or (X plus some multiple of P) where P is the pitch of the signatures as they leave the cutting cylinder. In this case, the first signature would be diverted to follow the long path and the next signature would follow the short path. The signatures would come together, one on top of the other as path xe2x80x9cAxe2x80x9d and path xe2x80x9cBxe2x80x9d converge before the transfer cylinder.
With this solution, the transportation and processing velocity of the signature can be reduced. The space between the signatures after they have been diverted into separate paths is large. This large space allows the signatures to be decelerated to a lower velocity. In the simple case of two paths, for example, the velocity of the signatures can be reduced to half of the velocity of the signatures at the exit of the cutting cylinder. The transfer cylinder can then rotate at one half the angular velocity that it would have had to rotate at otherwise. This significant reduction in velocity will improve the performance of the signature processing functions like fold-off.
In accordance with another feature of the invention, at least one of said tape paths has a spring-loaded tape roller for tensioning said tape path. In this way, the proper tape tension is maintained during changes which are made in the path length.
In accordance with a further feature of the invention, there is provided a tape roller contacting one of said tape paths, a pivot arm pivoting said tape roller about a pivot point, and an actuator pivoting said tape roller for changing the length of said tape path. The change in path length is accomplished in this way.
In accordance with an added feature of the invention, the at least two tape paths are three tape paths carrying first and second and third respective signatures, and said at least one collection point is two collection points, one of said collection points collecting the first and second signatures on top of one another and the other of said collection points collecting the first, second and third signatures on top of one another. This feature of the invention allows three signatures from the impression cylinder to be placed on top of one another.
FIG. 6 is a diagrammatic, side-elevational view of a pre-cylinder signature collector with a transport cylinder.
In accordance with an additional feature of the invention, at least one of said tape paths has a slowdown device for slowing down signatures on said tape path. The reduction in velocity improves the performance of signature processing functions such as fold-off.
In accordance with a concomitant feature of the invention, the at least two tape paths are three tape paths carrying first, second and third respective signatures, and said diverter station includes first and second diverters, said first diverter diverting the first and second signatures onto one of said tape paths and the third signature onto another of said tape paths, and said second diverter diverting the first and second signatures onto different tape paths. In this case, the sheets are diverted twice.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a pre-cylinder signature collector, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.